A global computer network, such as the Internet, provides an opportunity for advertisers to target Internet users within the network for marketing purposes. A user commonly searches for and browses content on the network by entering one or more search terms in a search query, typically implemented in search websites. The content that the user searches can include articles, web pages, emails, or other Internet accessible content containing the search term provided by the user. Many of the advertisements that the user is subjected to are based on search terms entered into a search engine.
The advertisements are generated by one or more agents, or advertisement engines, operating on web-servers for generating and displaying advertisements to users. Many search engines operate in cooperation with an advertisement engine, to display advertisements (ads) in response to the search terms entered by the user in the search query. The advertisement engine has a database of ads, from which the ads are selected based upon relevance to the search term provided by the user. In the case of paid search auctions, an advertiser bids on one or more search terms that relate to the ads. The paid search auction returns ads of the advertiser that are relevant to user queries according to the bidding search terms. For this, an advertiser needs to accurately match a user's query to the advertiser's search terms based on the relevancy of the search terms. Since each user can input widely varying search terms when searching for similar or identical search content, the matching of the user's query to the advertiser's search terms is difficult to achieve.